Jimmy Fallon, new host of “The Tonight Show” on NBC, knows what he wants to spend one of his first paychecks on -- a truck. And automakers are tripping over themselves to get him behind the wheel of one of their pickups.

The problem is that Fallon doesn’t know trucks that well.

On Wednesday night he asked his stage band, The Roots, if any of its members drove a truck and if they could help him out. But none did, so Fallon asked his audience about trucks.

One man yelled that he drove a Ford F-150. To which Fallon asked how big the truck was. The response he got became a running joke for the rest of the show: “Big enough.”

It took only minutes for Ford to jump on the offhand remark. The company took to Twitter to suggest a 2015 F-150 King Ranch, a truck that is not yet available to the public and might not be available for months.

Chrysler Group’s Ram brand went all in and created #GUTSGLORYFallon on Twitter, a medium that Fallon has used successfully on “Late Night” and now on “The Tonight Show,” and sent him messages throughout Thursday.

The brand even pulled up outside 30 Rockefeller Center in New York, where “The Tonight Show” is taped, in a silver Hemi-powered 2014 Ram 1500 crew cab with a sign on the back that read, “Big enough, Jimmy? Test it out.”

Fallon told his audience that he wanted to buy the truck himself, and didn’t want one given to him. In response, Ram pledged that if he chose the Chrysler Group truck, the brand would donate its sticker price to the charity of his choice.

The topic came up again Thursday night, when Fallon said that he still wanted a truck, and had narrowed his list down to 12 vehicles.

Fallon said that he might get a Nissan, GMC or a Toyota Tundra. He then said that a lot of people on Twitter were telling him to buy a Ford F-150.

He said Ram, which he incorrectly referred to as Dodge Ram, had a 1500 parked in front of the studio for a test drive. One of the band members took the test drive.

There is still no verdict from Fallon on which vehicle he may choose, but clearly the battle for Fallon's loyalty is gaining momentum.

And despite the automakers’ Twitter barrage, the Twitter accounts for “The Tonight Show” and Fallon himself have yet to respond to the sales pitches.